The present invention relates to an open end wrench capable of fast driving and, more particularly, to an open end wrench capable of fast driving a workpiece without the risk of undesired shifting from the workpiece.
U.S. Pat. No. 1,320,668 discloses a wrench including a stationary jaw and a movable jaw slideable along a guide. The movable jaw is forced against an abutment at an outer end of the guide by a spring bearing against the stationary jaw. An end of the spring is received in a bore in the stationary jaw. The other end of the spring is received in another bore in the movable jaw. An intermediate portion of the spring is exposed between the stationary jaw and the movable jaw. When the user intends to tighten or loosen a nut, the wrench is turned in a driving direction during which operation the movable jaw remains in contact with the abutment. For reengagement of the wrench with the nut, it is necessary only to turn the wrench in the opposite direction, during which operation the movable jaw slides backward against the pressure of the spring and on the edges of the nut. The movable jaw is forced forward again as soon as the bearing surfaces of the stationary and movable jaws are parallel with the sides of the nut. The nut can be tightened or loosened through repeated operations. However, the movable jaw wobbles, because the spring can not maintain the position of the movable jaw in a direction transverse to the sliding direction. Furthermore, the movable jaw is liable to disengage from the guide due to impact or falling to the ground. The spring will disengage from the wrench after disengagement of the movable jaw. Further, the exposed portion of the spring, when compressed by the movable jaw, is liable to bend and, thus, is in friction contact with the end edges of the bores of the stationary and movable jaws, leading to a non-smooth compression of the spring or even permanent deformation of the spring. Further, the exposed portion of the spring is apt to be contaminated by oil to which debris easily adheres, hindering movement of the movable jaw.
U.S. Pat. No. 3,695,125 discloses an open end ratchet wrench including a head having a fixed jaw and an opposed pawl support portion. A pawl and a spring are mounted to an inner side of the pawl support portion. The pawl is biased by the spring and slideable between an extended torquing position and a retracted ratcheting position. Two side caps are fixed to two sides of the head to define a space receiving the pawl and the spring and to prevent disengagement of the pawl and the spring. The pawl includes a stop shoulder to prevent the pawl from moving out of the pawl support portion under the action of the spring. However, the side caps may separate from the head when the wrench falls to the ground, causing disengagement of the pawl from the pawl support portion and subsequent failing of the spring. Furthermore, the pawl merely biased by the spring is still liable to wobble, although there are two side caps on opposite sides of the pawl. Further, the spring is liable to shift from its original position due to impingement to or repeated compression of an exposed portion of the spring, causing malfunction of the spring. Further, a gap exists between the side caps and the pawl when the pawl is moved into the space. Oil and debris may enter the gap and adversely affect the compression of the spring and the movement of the pawl.
U.S. Pat. No. 4,706,528 discloses an adjustable wrench including a fixed jaw and an adjustable jaw. In an embodiment, a sliding jaw portion is provided on the fixed jaw. The sliding jaw includes a rectilinearly extending slot through which a pin is extended, preventing disengagement of the sliding jaw. A plate spring is mounted to an inner face of the fixed jaw to bias the sliding jaw outward. A hole is formed in an end wall of the slot and receives a coil spring to bias the sliding jaw inward. Thus, the sliding jaw is movable inward or outward and can be retained in place under action of the plate spring and the coil spring. Such a wrench is particularly suitable for rotating pipes, but not suitable for tightening or loosening fasteners such as bolts, nuts, or the like. Specifically, since a pipe has no plane surfaces and is, thus, difficult to grip, the sliding jaw is moved outward to shorten the distance between the sliding jaw and the adjustable jaw for firmly clamping the pipe to permit tightening or loosening of the pipe. The sliding jaw is returned by moving inward under the action of the coil spring. Furthermore, the pipe causes inward movement of the sliding jaw and will not rotate when the wrench is rotated in a reverse direction. However, the coil spring is redundant when the wrench is utilized on a nut or bolt head that has flat sides. In the case that the wrench drives a nut or bolt head having flat faces in a reverse direction, the nut or bolt head initially permits the sliding jaw to move inward. However, when the jaw moves inward to its innermost position, the spacing between the sliding jaw and the adjustable jaw is still smaller than the spacing between two corners of the nut or bolt head such that the nut or bolt head will be rotated in the reverse direction, which is undesired. This is because the sliding jaw moves rectilinearly along the rectilinearly extending slot along an axis at a relatively small angle to a plane on which the adjusting jaw lies. Further, formation of a hole in the inner face of the fixed jaw for receiving a small screw to position the plate spring and formation of the hole for receiving the coil spring reduce the structural strength of the wrench such that the wrench can only be utilized for pipes that are hollow and, thus, exert smaller reactive force (which avoids deformation of the hollow pipes) when the pipes are rotated by the wrench. Further, although the coil spring has an end received in the hole of the sliding jaw, the other end of the coil spring outside of the hole is liable to bend when the spring is compressed, leading to friction at the end edge of the opening of the hole and resulting in non-smooth compression of the spring or even permanent deformation of the spring. Further, the slot is open such that most of the reactive force imparted to the sliding jaw during driving of a pipe or nut is transmitted to and, thus, damages the pin. This is because although the sliding jaw has a plane face in sliding contact with another plane face of the fixed jaw, the plane face of the sliding jaw can not provide guidance for the inward or outward movement of the sliding jaw. As a result, the plane face of the sliding jaw transmits the reactive force to the pin instead of effectively withstanding the torque.
U.S. Pat. No. 7,024,971 discloses an open end ratchet wrench including first and second stationary jaws. The first stationary jaw supports a movable plate. A space is sandwiched between two face plates of the first stationary jaw to accommodate the movable plate. The movable plate includes two angled slots each receiving a pin extending through the space, avoiding disengagement of the movable plate. The wrench further includes a hole receiving a spring that has an end located outside of the hole for biasing the movable plate. Each angled slot of the movable plate includes a short section and a long section at an angle to the short section such that the movable plate can move in two stages each having a rectilinear travel. Although the two-stage movement of the movable plate increases the spacing between the movable plate and the second stationary jaw, the movable plate is liable to get stuck at the intersection of the long and short sections, adversely affecting operation of the wrench in the reverse direction. Furthermore, the spring has an exposed section that is liable to bend when the spring is compressed, leading to friction at the end edge of the opening of the hole and resulting in non-smooth compression of the spring or even permanent deformation of the spring. Further, the angled slots increase the area of the movable plate or the first stationary jaw, resulting in difficulties in reducing the volume of the open end wrench. Thus, the wrench can not be used in a small space. If the area of the movable plate is increased or the first stationary jaw is reduced in size, the short section or the longer section would be exposed outside of the first stationary jaw such that debris is apt to accumulate in the slots, adversely affecting rectilinear movement of the movable plate. Further, since the space is open in both sides, the reaction force imparted to the movable plate during driving of a workpiece is completely transmitted to the pins that can not withstand high torque. As a result, the wrench can not be used in a high-torque driving operation.
U.S. Publication No. 2009/0193941 A1 discloses first and second jaws formed on a jaw support. The first jaw can be moved by rotating a worm. The jaw support includes an open track in the form of a slot receiving the second jaw. The jaw support further includes a pin extending through the track. The second jaw includes a rectilinear opening through which the pin extends, preventing the second jaw from disengaging from the jaw support. A biasing member is mounted in the opening of the second jaw to bias the second jaw outward. Since the second jaw includes a single rectilinear opening, a change in the spacing from the second jaw to the first jaw is relatively small such that a workpiece will be rotated when the wrench rotates in a reverse direction not intended to rotate the workpiece. Thus, the first jaw must be movable, and the spacing between the first and second jaws can be adjusted by rotating the worm to avoid joint rotation of the workpiece when the wrench rotates in the reverse direction. However, the wrench of this type includes many elements, and the track, opening, and holes in the elements weaken the wrench. Furthermore, since the track is open, the reaction force imparted to the second jaw during driving of the workpiece is completely transmitted to the pin. Thus, the pin is liable to be damaged. Although the second jaw includes a surface in sliding contact with the jaw support to guide sliding movement of the second jaw, this surface merely transmits the reactive force to the pin instead of effectively withstanding the torque. Further, since the second jaw moves rectilinearly, the opening in the second jaw must be lengthened if it is desired to increase the spacing between the first and second jaws. However, this would expose the opening support such that the opening and the biasing member in the opening would easily be contaminated by oil to which debris adheres easily. Furthermore, operation of the biasing member would be adversely affected, causing non-smooth movement of the second jaw.
U.S. Patent Publication No. US 2010/0071516 A1 discloses a reciprocatable open end wrench including first and second jaws and a swing member. The second jaw includes a concave arcuate surface having a slot. The swing member is received in the slot. A surface of the swing member faces the second jaw and has an arcuate hollow groove for receiving a returning device. A retaining pin is inserted into the hollow groove in a manner allowing the swing member to be slideable relative to the second jaw. The returning device presses against the retaining pin and the swing member and, thus, biases the swing member outward. However, the swing member has a complicated outline and, thus, requires troublesome processing. Furthermore, the concave arcuate surface reduces the width of the second jaw and, thus, weakens the structure of the second jaw and causes stress concentration on the concave surface.
Thus, a need exists for an open end wrench capable of fast driving of a workpiece without the disadvantages of the above conventional open end wrenches.